You will be given a definition of a task first, then some input of the task.
Based on the information present in the given passage, you need to write a correct answer to the given question. A correct answer is one that correctly and completely answers the question. Do not write answers that address the question partially or incorrectly. The correct answer must be contained in the given paragraph.

Paragraph- Sent 1: If you have a mass of 50 kg on Earth, what is your weight in newtons?
Sent 2: An object with more mass is pulled by gravity with greater force.
Sent 3: Mass and weight are closely related.
Sent 4: However, the weight of an object can change if the force of gravity changes.
Sent 5: On Earth, the force of gravity is the same everywhere.
Sent 6: So how does the force of gravity change?
Sent 7: It doesnt if you stay on Earth.
Sent 8: What if we travel to another planet or moon in our solar system?
Sent 9: Look at the photo of astronaut Edwin E. Aldrin Jr. taken by fellow astronaut Neil Armstrong in the Figure.
Sent 10: They were the first humans to walk on the moon.
Sent 11: An astronaut weighs less on the moon than he would on Earth.
Sent 12: This is because the moons gravity is weaker than Earths.
Sent 13: The astronauts mass, on the other hand, did not change.
Sent 14: He still contained the same amount of matter on the moon as he did on Earth.
Sent 15: If the astronaut weighed 175 pounds on Earth, he would have weighed only 29 pounds on the moon.
Sent 16: If his mass on Earth was 80 kg, what would his mass have been on the moon?
Sent 17: [Figure 3]. 
Question: When does the force of gravity change.
Output:
On another planet or moon in the solar system.